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Abstract

Investigation of Low Profile Antenna Designs
for Use in Hand-Held Radios

Andrew T. Gobien

(ABSTRACT)

Antennas in hand-held radios must be compact and unobtrusive. Electrically small and low-
profile antennas experience high input reactance, low input resistance, and low radiation efficiency.
Further degradation of radiation efficiency occurs in hand-held radios due to size-reduced ground planes, losses within the plastic device casing, and losses due to coupling with the tissue of the user. These factors
may also affect the radiation pattern of the antenna.

This discussion reports on antenna designs that are well suited for hand-held radios. The design
issues are covered for electrically small antennas and the hand-held environment. A review of Microstrip
Antenna (MSA) theory, and the theory of the Inverted-L Antenna (ILA), and variations on the ILA
including the Inverted-F Antenna (IFA), Planar Inverted-F Antenna (PIFA), and Dual Inverted-F Antenna
(DIFA) is included. Two specific antenna designs are presented: the DIFA and the Proximity-Coupled
Rectangular Patch MSA. The radiation patterns and input impedance of the DIFA are calculated
numerically and measured empirically. The Proximity-Coupled Rectangular Patch Microstrip Antenna is
treated numerically.